Periodic light flasher



United States Patent M 3,297,910 PERIODIC LIGHT FLASHER Bernard J.Gershen, Edison, N.J., assignor to General Motors Corporation, Detroit,Mich., a corporation of Delaware Filed Dec. 31, 1963, Ser. No. 334,760 2Claims. (Cl. 315-155) This invention relates in general to signalingdevices and more particularly to an improved flasher circuit.

Circuits for periodically connecting and disconnecting a load circuit toand from a source of electrical power are well known and find wideapplication. In particular the load circuit may consist of one or moreelectric lamps which are turned on and oil in sequence and is generallyknown as a flasher.

In flasher circuits and other periodic switching circuits known to theart heretofore, unilateral control devices have commonly been employedto effect controlled operation of switches, or the switches have beenactuated by motors or other mechanical timing devices. Systems employingunilateral control devices such as vacuum tubes or transistors lack therequisite reliability where the system must operate without supervisionover extremely long time periods. They are, moreover, relativelyexpensive and their timing cycles tend to vary with aging of theunilateral control device and other circuit components associated withthe latter. Motor control devices on the other hand tend to berelatively expensive and are subject to wear and require maintainance sothat their utilization in unattended or unsupervised installationsdesigned for automatic operation over long periods of time isinadvisable.

The disadvantages associated with the prior art flasher circuit areobviated by the present invention which provides a flasher which haslong life, is not subject to a high degree of maintenance and can befabricated economically in a package of very small size.

In accordance with the present invention a high power cadmium sulfidephotocell is mounted in close proximity with a neon tube in a lighttight enclosure. The photocell is connected in series with anincandescent lamp across a source of A.C. voltage. A rectifier, aresistor, and a capacitor are connected across the source, the capacitorbeing connected in shunt with the neon tube. The capacitor isperiodically charged to the ionizing potential of the neon tube causingthe neon tube to periodically flash and lower the resistance of thephotocell to energize the incandescent lamp.

A more complete understanding of the present invention may be had fromthe following detailed description which should 'be read in conjunctionwith the accompanying drawing in which:

FIGURE 1 is a schematic circuit diagram of the flasher circuit inaccordance with the present invention;

FIGURE 2 is a schematic circuit diagram of a modification of the circuitof FIGURE 1.

Referring now to the drawing and initially to FIG- URE 1, there is shownone embodiment of the present invention in which the numeral designatesa cadmium sulfide power photocell (Delco Radio type LDR-25) connected inseries with a load which in this instance is a 6 watt incandescent lamp12. The photocell 10 and the lamp 12 are connected across a 115 voltA.C. source of power. The photocell 10 is mounted within an enclosure 14and in close proximity to a neon lamp 1-6. A charging circuit for theneon tube 16 comprises a low current rectifier 18 providing a pulsatingDC. output to a resistor 20 and a capacitor 22.

3,297,910 Patented Jan. 10, 1967 The operation of the circuit shown inFIGURE 1 is as follows. It will be understood that when no lightimpinges the photocell 10, it presents a very high resistance in serieswith the incandescent lamp 12 causing the lamp 12 to be deenergized.With the flasher circuit connected to the A.C. source, the capacitor 22will begin to charge at a rate determined by the value of resistor 20.When the capacitor 22 charges to the ionizing potential of the neon lamp16, the lamp 16 will fire thereby illuminating the photocell 10 anddrastically reducing its resistance. The reduced resistance of thephotocell 10 causes the lamp 12 to be energized. When the neon lamp 16fires, the capacitor 22 will discharge therethrough extinguishing theneon lamp 16 and the cycle will then be repeated.

Referring now to FIGURE 2, a modification of the present invention isshown. An additional incandescent lamp 24 is connected in series with asecond cadmium sulfide power photocell 26 across the source of power.The lamp 12 and the photocell 26 are disposed in close proximity witheach other within a light tight enclosure 28.

When a circuit is connected to the volt A.C. source, a pulsating DC.voltage appears across the parallel circuit consisting of capacitor 22and a neon lamp 16. Because the ionizing potential of the neon lamp 16is greater than 60 volts, it presents a higher resistance to thepulsating DC. voltage than capacitor 22 which consequently charges at arate determined by the value of resistor 20.

When the potential across the capacitor 22 reaches the ionizingpotential of the neon lamp 16, it fires and illuminates the photocell 10until the potential across capacitor 22 dissipates through the neon lamp16 to such a value that the neon lamp 16 can no longer maintain itsionized condition.

When the photocell 10 conducts, incandescent lamp 12 illuminatesphotocell 26 at a level much higher than that which falls on photocell10. Consequently, photocell 26 passes far more current than photocell 10and lamp 24 attains virtually full brilliance.

Upon the extinction of neon lamp 1 6, capacitor 22 again charges to thefiring potential of the neon lamp 16 and the entire cycle continuesrepeatedly. The chain of lamps and cells provides a regenerative effectwhich for practical purposes constitutes light amplification.

Although the description of this invention has been given with respectto a particular embodiment, it is not to be construed in a limitingsense. Many variations and modifications within the spirit and scope ofthe invention will now occur to those skilled in the art. For adefinition of the invention, reference is made to the appended claims.

I claim:

1. A high voltage flasher operated from an A.C. source comprising a highpower photocell connected in series with a lamp across said source,means for periodically illuminating said photocell to lower theresistance thereof and periodically energize said lamp, said meanscomprising a diode, a resistor, and a capacitor connected across saidsource and a neon lamp in shunt with said capacitor, said photocell andsaid neon tube being located in a light tight enclosure and in closeproximity to each other, said neon lamp having a predetermined ionizingpotential, said capacitor being periodically charged to said ionizingpotential thereby energizing said neon lamp to illuminate said photocelland cause energization of said lamp.

2. An A.C. flasher circuit comprising a series circuit including acapacitor, a resistor, and a diode connected across a source of A.C.voltage, a neon lamp connected in shunt with said capacitor, a seriescircuit including a high power photocell and an incandescent lampconnected across said source, a series circuit including a secondphotocell and a second incandescent lamp connected across said source,said neon lamp and said first photocell being mounted in close proximitywith each other within a light tight enclosure, said incandescent lampand said second photocell being mounted in close proximity with eachother Within a second light tight enclosure.

References Cited by the Examiner UNITED STATES PATENTS 2,838,719 6/1958Chitty 315158 2,905,862 9/1959 Giuffrida 315156 3,062,961 11/1962 Kalnset a1. 250206 3,206,650 9/1965 Miller et al. 315-449 JAMES W. LAWRENCE,Primary Examiner. R. SEGAL, Assistant Examiner..

1. A HIGH VOLTAGE FLASHER OPERATED FROM AN A.C. SOURCE COMPRISING A HIGHPOWER PHOTOCELL CONNECTED IN SERIES WITH A LAMP ACROSS SAID SOURCE,MEANS FOR PERIODICALLY ILLUMINATING SAID PHOTOCELL TO LOWER THERESISTANCE THEREOF AND PERIODICALLY ENERGIZE SAID LAMP, SAID MEANSCOMPRISING A DIODE, A RESISTOR, AND A CAPACITOR CONNECTED ACROSS SAIDSOURCE AND A NEON LAMP IN SHUNT WITH SAID CAPACITOR, SAID PHOTOCELL ANDSAID NEON TUBE BEING LOCATED IN A LIGHT TIGHT ENCLOSED AND IN CLOSEPROXIMITY TO EACH OTHER, SAID